In a battery pack that includes a battery cell accommodated in a sealed case, it is necessary to reduce the internal pressure in the sealed case when the internal pressure in the sealed case is increased. For example, a sealing type rechargeable battery disclosed in Patent Document 1 includes a box-like battery jar including a plurality of successively provided battery jar members. Each battery jar member accommodates a group of electrode plates with electrolytic solution. A gas collective portion is provided in the box-like battery jar. Between the gas collective portion and each battery jar member, a gas discharge portion, which opens if the internal pressure in each battery jar member is greater than or equal to a predetermined pressure, is provided. A gas outlet, which conducts the gas to the outside, is provided in the gas collective portion. If gas is generated in each battery jar member and the internal pressure increases, the gas is discharged through a gas discharge port to the gas collective portion. This reduces the internal pressure of each battery jar member. The gas discharged to the gas collective portion is conducted to the outside through the gas outlet.